Output* output) {
    *output = ToOutput(while_ctx->cond_output());
    return absl::OkStatus();
  };

  // Body function that adds one to input.
  BodyGraphBuilderFn body_fn = [](const Scope& scope,
                                  const std::vector<Output>& inputs,
                                  std::vector<Output>* outputs) {
    DCHECK_EQ(inputs.size(), 1);

    results: a list of futures.
    body_fn: input is [predicate_promise, arg0_future, arg0_promise, arg1_future, arg1_promise, ..., invariant_args] and has no returned results.
  }];

  let arguments = (ins TF_Tensor:$cond,
                       Variadic<TF_Tensor>:$arguments,
                       FlatSymbolRefAttr:$body_fn,
                       I32Attr:$invariant_size);

      last element of results is an I1 value that is false.
    body_fn: The body function that takes the arguments and returns the results
      that includes an I1 value to indicate whether next iteration should be executed.

    The pseudo code:

    while(cond) {
      results = body_fn(operands)
      cond = results#1
    }
    return results

  }];

	var extOff, bodyOff int
	if typ == syscall.NET_RT_IFLISTL {
		if len(b) < 20 {
			return nil, errMessageTooShort
		}
		extOff = int(nativeEndian.Uint16(b[18:20]))
		bodyOff = int(nativeEndian.Uint16(b[16:18]))
	} else {
		extOff = w.extOff
		bodyOff = w.bodyOff
	}
	if len(b) < extOff || len(b) < bodyOff {
		return nil, errInvalidMessage
	}

func probeRoutingStack() (int, map[int]*wireFormat) {
	var p uintptr
	rtm := &wireFormat{extOff: 40, bodyOff: sizeofRtMsghdrDragonFlyBSD4}
	rtm.parse = rtm.parseRouteMessage
	ifm := &wireFormat{extOff: 16, bodyOff: sizeofIfMsghdrDragonFlyBSD4}
	ifm.parse = ifm.parseInterfaceMessage
	ifam := &wireFormat{extOff: sizeofIfaMsghdrDragonFlyBSD4, bodyOff: sizeofIfaMsghdrDragonFlyBSD4}
	ifam.parse = ifam.parseInterfaceAddrMessage

		if compatFreeBSD32 {
			ifm.bodyOff = sizeofIfMsghdrFreeBSD7Emu
		} else {
			ifm.bodyOff = sizeofIfMsghdrFreeBSD7
		}
	case 800000 <= rel && rel < 900000:
		if compatFreeBSD32 {
			ifm.bodyOff = sizeofIfMsghdrFreeBSD8Emu
		} else {
			ifm.bodyOff = sizeofIfMsghdrFreeBSD8
		}
	case 900000 <= rel && rel < 1000000:
		if compatFreeBSD32 {
			ifm.bodyOff = sizeofIfMsghdrFreeBSD9Emu
		} else {

	rtm := &wireFormat{extOff: 36, bodyOff: sizeofRtMsghdrDarwin15}
	rtm.parse = rtm.parseRouteMessage
	rtm2 := &wireFormat{extOff: 36, bodyOff: sizeofRtMsghdr2Darwin15}
	rtm2.parse = rtm2.parseRouteMessage
	ifm := &wireFormat{extOff: 16, bodyOff: sizeofIfMsghdrDarwin15}
	ifm.parse = ifm.parseInterfaceMessage
	ifm2 := &wireFormat{extOff: 32, bodyOff: sizeofIfMsghdr2Darwin15}
	ifm2.parse = ifm2.parseInterfaceMessage

	rtm := &wireFormat{extOff: 40, bodyOff: sizeofRtMsghdrNetBSD7}
	rtm.parse = rtm.parseRouteMessage
	ifm := &wireFormat{extOff: 16, bodyOff: sizeofIfMsghdrNetBSD7}
	ifm.parse = ifm.parseInterfaceMessage
	ifam := &wireFormat{extOff: sizeofIfaMsghdrNetBSD7, bodyOff: sizeofIfaMsghdrNetBSD7}
	ifam.parse = ifam.parseInterfaceAddrMessage
	ifanm := &wireFormat{extOff: sizeofIfAnnouncemsghdrNetBSD7, bodyOff: sizeofIfAnnouncemsghdrNetBSD7}

	nativeEndian.PutUint32(b[20:24], uint32(m.Seq))
	attrs, err := marshalAddrs(b[w.bodyOff:], m.Addrs)
	if err != nil {
		return nil, err
	}
	if attrs > 0 {
		nativeEndian.PutUint32(b[12:16], uint32(attrs))
	}
	return b, nil
}

func (w *wireFormat) parseRouteMessage(typ RIBType, b []byte) (Message, error) {
	if len(b) < w.bodyOff {
		return nil, errMessageTooShort
	}
	l := int(nativeEndian.Uint16(b[:2]))

		extOff:  w.extOff,
		raw:     b[:l],
	}
	a, err := parseLinkAddr(b[w.bodyOff:])
	if err != nil {
		return nil, err
	}
	m.Addrs[syscall.RTAX_IFP] = a
	m.Name = a.(*LinkAddr).Name
	return m, nil
}

func (w *wireFormat) parseInterfaceAddrMessage(_ RIBType, b []byte) (Message, error) {
	if len(b) < w.bodyOff {
		return nil, errMessageTooShort
	}
	l := int(nativeEndian.Uint16(b[:2]))
	if len(b) < l {